/**
 * Copyright (C) 2006 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.inject.internal.util;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;

import java.util.List;

/**
 * Provides access to the calling line of code.
 * 
 * @author crazybob@google.com (Bob Lee)
 */
public final class SourceProvider {

    /** Indicates that the source is unknown. */
    public static final Object UNKNOWN_SOURCE = "[unknown source]";

    private final SourceProvider parent;
    private final ImmutableSet<String> classNamesToSkip;

    public static final SourceProvider DEFAULT_INSTANCE = new SourceProvider(ImmutableSet.of(SourceProvider.class.getName()));

    private SourceProvider(Iterable<String> classesToSkip) {
        this(null, classesToSkip);
    }

    private SourceProvider(SourceProvider parent, Iterable<String> classesToSkip) {
        this.parent = parent;

        ImmutableSet.Builder<String> classNamesToSkipBuilder = ImmutableSet.builder();
        for (String classToSkip : classesToSkip) {
            if (parent == null || !parent.shouldBeSkipped(classToSkip)) {
                classNamesToSkipBuilder.add(classToSkip);
            }
        }
        this.classNamesToSkip = classNamesToSkipBuilder.build();
    }

    /** Returns a new instance that also skips {@code moreClassesToSkip}. */
    public SourceProvider plusSkippedClasses(Class... moreClassesToSkip) {
        return new SourceProvider(this, asStrings(moreClassesToSkip));
    }

    /** Returns true if the className should be skipped. */
    private boolean shouldBeSkipped(String className) {
        return (parent != null && parent.shouldBeSkipped(className)) || classNamesToSkip.contains(className);
    }

    /** Returns the class names as Strings */
    private static List<String> asStrings(Class... classes) {
        List<String> strings = Lists.newArrayList();
        for (Class c : classes) {
            strings.add(c.getName());
        }
        return strings;
    }

    /**
     * Returns the calling line of code. The selected line is the nearest to the top of the stack that
     * is not skipped.
     */
    public StackTraceElement get(StackTraceElement[] stackTraceElements) {
        Preconditions.checkNotNull(stackTraceElements, "The stack trace elements cannot be null.");
        for (final StackTraceElement element : stackTraceElements) {
            String className = element.getClassName();

            if (!shouldBeSkipped(className)) {
                return element;
            }
        }
        throw new AssertionError();
    }

    /**
     * Returns the non-skipped module class name.
     */
    public Object getFromClassNames(List<String> moduleClassNames) {
        Preconditions.checkNotNull(moduleClassNames, "The list of module class names cannot be null.");
        for (final String moduleClassName : moduleClassNames) {
            if (!shouldBeSkipped(moduleClassName)) {
                return new StackTraceElement(moduleClassName, "configure", null, -1);
            }
        }
        return UNKNOWN_SOURCE;
    }
}
